Radio receiving system



Jan. 29, 1-929.

. G. L. BEER$ RADIO RECEIVING SYSTEM FiledFeb. '10, 1925 Fig.1.

' Fig.2.

INVENTOR WITNESSES:-

George L. Beers ATTbRNEY Patented Jan. 29, 1929.

UNITED STATES PATENT OFFICE.

GEORGE L. BEERS, OF WILKINSBUBG, PENNSYLVANIA, ASS IGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

RADIO RECEIVING SYSTEM.

v Application filed February My invention relates to radio receiving systems and particularly to radio receiving sys tems comprising loop antennae.

It is an object of my invention to construct a radio receiving system provided with loop antennae and having means for preventing the re-radiation of local oscillatory energy from the loopa Another of my invention is to construct a radio receiving system comprising a loop antenna, and superheterodyne receiving apparatus in which the re-radiation of the oscillations of the local heterodyne oscillation generator is eifectually prevented;

In the operation of radio receiving systems adapted to be combined with a loop antenna, difficulty has been experienced with'the reradiation of oscillatory energy from the loop, especially when the connected apparatus is of the superheterodyne type having a local oscillation generator therein.

My invention provides means whereby the introduction of local oscillations in the loop antenna is compensated for and the radiation of energy therefrom is prevented.

Other objects and structural details of my invention will be apparent from the follow ing description when read in connection with the accompanying drawings. wherein:

Figure 1 is a diagr-nnmatic representation of circuits and apparatus embodying a pre ferred form of my invention, and

Fig. 2 is a diagrammatic representation of an alternative embodiment.

Referring to Fig. 1, a loop antenna 1 is connected to a triode 2. The loop 1 has connected across the'terminals thereof a tuning condenser ()ne of the terminals of the loop 1 is connected to the grid of the triode 2. The other terminal of the loop 1 is connected through a balancing condenser 5 to the anode of the triode-2. A parallel resonant circuit 4:.is connected to one terminal of the cathode stray fields of the 100 10, 1925. Serial No. 8,208.

former 9 to a detector triode 11 and signal translating-means 12.

In the operation of the system, incoming signal energy causes the I resonant circuit, comprising the loop 1 and the condenser 3, to oscillate when the natural resonant period of the system is substantially the same as that of the incoming signals. The resonant oscillation thus produced, develops potential differences across the condenser 3 and across the terminals of the loop 1. One-half of the developed potential is impressed between the grid and cathode of triode 2 by way of the grid connected end of the loop 1 and the midpoint, through the parallel resonant circuit 4. The presence of the circuit 4 and the coil 6 inductively associated therewith provides the combination of circuits needed for the production of self-oscillation of the triode 2. The frequency of this self-oscillation is determined by the natural resonant frequency of the circuit 4; which may be made different from the frequency to which the combination ofthe loop 1 and condenser 3 are tuned, thereby producing beat phenomena when combined with the signal oscillations. These beat phenomena are resolved by the triode and associated circuits into oscillations of a different radio frequency which is the same as the beat frequency, and which are modulated similarly to the original signals and are adjusted to occur in the system at the frequency to which the oscillation transformer and triode 8 are tuned.

The tuning of the resonant circuit 4 should desirably be such that its fundamental frequency isone-half of the frequency required to heterodyne the incoming signals for the production of the desired beat frequency. The harmonic of the fundamental frequency of the generator then heterodynes the incoming signals in the usual way. This use of the harmonics has been found desirable in order to prevent improper reaction between the antenna 1 and the resonant circuit 4 whic 1 tend, when the fundamental fre uency is used, to develop troublesome inte ering frequencies that make the operation of the device less certain.

The beat oscillations are amplified in the cutomary way, detected by triode 11 and its associated circuits and translated into sound by receivers 12.

The triode 2 is set into self-oscillation by energy transferred from coil 6 through circuit 4 and the midpoint of loop 1, half of the turns of loop 1, to the grid of triode 2. This enel g'y, however, is susceptible to re-radiation therefrom. The presence of a connection between the other terminal of loop 1 and anode of triode2 results in a path for energy through i the other half of the turns of loop 1, to the grid of triode 2.

By making the capacitance of the balancing condenser 5 substantially equal to the capacitance between the grid and the cathode of the triode 2, substantially equal amounts of energy are allowed to flow through both halves of the loop 1. These equal increments of energy flow in opposite directions through loop 1, are substantially 180 degrees out of phase and the ma netic fields produced thereyin loop 1 are su stantially neutralized and, thereby, no radiation therefrom occurs.

In the alternative embodiment shown in Fig. 2, a separate oscillation generator is provided, consistin of a triode 13, a resonant circuit 14 coup ed to a plate coil 15, and an output coil 16. The coil 16 is coupled to a coil 17, which is substituted for the circuit 4 of F i 1 and is connected between the center tap o the loop 1 and the cathode circuit of the triode 2. The system of Fig. 2 operates in a similar manner,.except that the oscillatory energy is furnished by the local generator comprising the triode 13 instead of by the self oscillation of the triode 2.

While I have shown but two embodiments of my invention in the accompanying drawing, it is capable of various changes and modifications therefrom without departing from the spirit thereof and it is desired, therefore, that only such limitations shall be placed thereon as'are imposed by the prior-art or indicated in the appended claims.

I claim as my invention 1. A radio receiving system, comprising a loop antenna having a plurality of turns of conductor and three terminals connected respectively to the ends of said conductor and a point therein near the center thereof, a tuntion of the connection to said center terminal, whereby beat frequency phenomena with received signals are produced, and amplifying and detecting means adapted to strengthen said beat frequency phenomena and translate them into signals.

2. In a radio receiving system, ,a signalre;eiving antenna comprising an inductance, anoscillation generator adjusted to generate oscillations of different frequency from those impressed upon the antenna by the signal and connections whereby the oscillations from said oscillation generator are caused to flow through two portions of saidinductance in parallel. f

3. A radio receiving system comprising a loop-antenna, a thermionic device having cathode, grid and plate electrodes, a connection from one terminal of said loop antenna to said grid, a connection including a stop-; I

ping condenser between the other terminal of said loop antenna and said anode, a connec-' tion between an intermediate point on said loop-antenna and said cathode, an oscillation generator, and means whereby said oscillation generator may impress potentials between said intermediate point and said catha ode, whereby beat-phenomena may be caused between incoming signals and the generated oscillations without permitting the radiation of said oscillations by said loop-antenna.

In testimony whereof. I have hereunto subscribed my name this 3rd day of February,

' GEORGE L. 'BEERS. 

